Calibration system including separation vessel and pipeline

ABSTRACT

A closed loop system for the calibration of a multiphase meter, such as a multiphase flow meter or water cut meter, and a method of employing the system in calibration of multiphase meters in crude oil production processes. The system includes an oil and water separation vessel, oil and water flow meters, valves, pumps, and a single phase calibration unit. The system employs a two-step calibration process. First internal single phase oil and water meters are calibrated using the single phase calibration unit; subsequently multiphase meter calibration is achieved using the two precalibrated single phase flow meters.

BACKGROUND OF THE INVENTION Technical Field

The present disclosure relates to a system and method for thecalibration of a multiphase meter, such as a multiphase flow meter or awater cut meter employing a closed loop multiphase flow system.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Liquid measuring devices are used in a wide variety of commercialapplications. The measurement of two-phase of multiphase flow quantitiesis essential for the understanding of many technical processes. It is achallenge in the petroleum industry to measure the fluid mixture flowrate accurately in crude oil. The complex nature of the crude oilmixture makes it difficult to measure the fluid mixture flow rate andcontent of a multiphase fluid. The conventional two phase measurementsystems require separation of the two phases (i.e. oil and water) whichresults in the interruption of the continuous industrial process. Tomeasure the water content in multiphase fluids, phase fraction and phasevelocity measurement devices are generally used. In addition, a Venturimeter is frequently used for the flow rate measurement of the multiphasemixture which necessitates the accurate measurement of fluid mixturedensity as an input parameter for determination of the fluid flow rate.Over the last decade, the measurement of multi-phase flow has been afocus of attention in the oil and gas industry. A number of multiphasemeters or multiphase flow meters (MPFMs) have been developed. Theavailable meters are very expensive and are not accurate enough to givethe desired results.

Major oil producers in the world require large quantities of multiphaseflow meters to operate and manage oil fields and reservoirs. Multiphaseflow meters are highly sophisticated devices and involve hugeinvestments. Being a major consumer of multiphase flow meters, oilproducers will be the beneficiary of any such system which is simple touse, easy to operate and at the same time, accurately calibratesmultiphase meters such as multiphase flow meters and water cut meters.

In view of the forgoing, one object of the present disclosure is toprovide an accurate multiphase meter calibration system that employs atwo-step calibration process. First, calibrating internal single phaseoil and water meters by using a single phase calibration unit, andsecond, calibration of a multiphase meter using the two precalibratedsingle phase flow meters. A further aim of the present disclosure is toprovide a method for calibrating a multiphase meter, such as amultiphase flow meter or water cut meter, using the system as describedherein.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the present disclosure relates to a closedloop system for calibration of a multiphase meter comprising i) aseparation vessel, comprising a first compartment for containing waterand a second compartment for containing oil, ii) a first junctionlocated downstream of the separation vessel having a first input, asecond input, and an output, iii) a water pipeline configured to receivewater from the first compartment and deliver it to the first input ofthe first junction, iv) an oil pipeline configured to receive oil fromthe second compartment and deliver it to the second input of the firstjunction, v) a multiphase meter section comprising the multiphase meterto be calibrated located downstream of the output of the first junction,vi) a second junction located downstream of the multiphase meter sectionhaving an input configured to receive water, oil or both from themultiphase meter section, a first output and a second output, vii) asingle phase calibration unit located downstream of the second junctionand upstream of the separation vessel, viii) a single phase pipelinelocated downstream of the second junction configured to receive water oroil from the first output of the second junction and deliver it to theseparation vessel through the single phase calibration unit, and ix) amultiphase collecting pipeline located downstream of the second junctionconfigured to receive water and oil from the second output of the secondjunction and deliver it to the separation vessel without passing throughthe single phase calibration unit, wherein the separation vessel, thefirst junction, the multiphase meter section, the second junction, andthe single phase calibration unit are fluidly connected, wherein thewater pipeline and oil pipeline are connected in parallel between theseparation vessel and the first junction, and wherein the single phasepipeline and the multiphase collecting pipeline are connected inparallel to the second junction.

In one embodiment, the multiphase meter to be calibrated is a multiphaseflow meter.

In one embodiment, the multiphase meter to be calibrated is a water cutmeter.

In one embodiment, the single phase calibration unit comprises i) acalibration tank having a fluid reference level and a maximum fluidlevel configured to collect an amount of water or an amount of oil fromthe single phase pipeline, ii) a fluid level sensor configured to detecta level of water or a level of oil in the calibration tank and iii) afluid level sighting glass configured to visualize a level of water or alevel of oil in the calibration tank.

In one embodiment, the water pipeline comprises a variable flow waterpump downstream of the first compartment and a water flow meterdownstream of the variable flow water pump and the oil pipelinecomprises a variable flow oil pump downstream of the second compartmentand an oil flow meter downstream of the variable flow oil pump.

In one embodiment, the system further comprises a data acquisition unitcomprising a microprocessor configured to collect and process data fromand electronically connected to at least one of the water flow meter,the oil flow meter, the fluid level sensor of the single phasecalibration unit and the multiphase section comprising the multiphasemeter to be calibrated.

In one embodiment, the system further comprises a flow controllerconfigured to control the speed of at least one of the variable flowwater pump and the variable flow oil pump and receive data from at leastone of the water flow meter and the oil flow meter.

In one embodiment, the single phase pipeline further comprises at leastone solenoid valve located upstream of the single phase calibration unitand the multiphase collecting pipeline further comprises at least onesolenoid valve located upstream of the separation vessel.

In one embodiment, the system further comprises a third junction locateddownstream of the single phase calibration unit having a first inputconfigured to receive water or oil from the single phase pipe, a secondinput configured to receive water, oil or both from the multiphasecollecting pipeline, and an output configured to deliver water, oil orboth to the separation vessel.

In one embodiment, the single phase pipeline further comprises a fixedflow fluid return pump located downstream of the single phasecalibration unit and upstream of the third junction.

In one embodiment, the single phase pipeline further comprises at leastone solenoid valve located downstream of the single phase calibrationunit and upstream of the fixed flow fluid return pump.

In one embodiment, the system further comprises a programmable logiccontroller configured to control the operation of at least one of thevariable flow water pump, the variable flow oil pump, the fixed flowfluid return pump, and at least one of the solenoid valves.

In one embodiment, the water pipeline further comprises one or morevalves located downstream of the water flow meter, upstream of thevariable flow water pump or both and the oil pipeline further comprisesone or more valves located downstream of the oil flow meter, upstream ofthe variable flow oil pump or both.

In one embodiment, the separation vessel is a cylindrical oil-watergravity separator and the first compartment and the second compartmentare separated by a weir having a height of 0.5 to 0.8 times the diameterof the cylinder.

In one embodiment, the single phase calibration unit further comprises adrain gate valve and a removable lid.

According to a second aspect, the present disclosure relates to a methodfor calibrating a multiphase meter employing the system in any of itsembodiments comprising i) measuring and setting a water flow rate at apredetermined value by flowing water from the first compartment to thesingle phase calibration unit through the multiphase meter section, ii)measuring and setting an oil flow rate at a predetermine value byflowing oil from the second compartment to the single phase calibrationunit through the multiphase meter section, iii) combining water from thefirst compartment at the predetermined water flow rate value and oilfrom the second compartment at the predetermined flow rate value to forma multiphase stream downstream of the first junction, iv) flowing themultiphase stream through the multiphase meter section to the multiphasecollecting pipeline, v) measuring the flow rate of the multiphase streamby means of the multiphase flow meter to be calibrated, and vi)processing the obtained data of the multiphase stream flow rate alongwith the predetermined water flow rate value and the predetermined oilflow rate value to calculate a calibration correction factor.

In one embodiment, the method further comprises recycling at least oneof the water, the oil and the multiphase stream to the separation vesselthrough the single phase pipeline or the multiphase collecting pipeline.

In one embodiment, the method further comprises calibrating a water flowmeter, an oil flow meter or both.

In one embodiment, at least one of a data acquisition system, aprogrammable logic controller and a flow controller is used in at leastone of the flowing, the measuring, and the setting of the water flowrate, the oil flow rate or both.

In one embodiment, the multiphase meter to be calibrated is at least oneselected from the group consisting of a multiphase flow meter and awater cut meter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is an exemplary illustration of a multiphase meter calibrationsystem 161, according to certain embodiments.

FIG. 2 is an exemplary illustration of a single phase calibration unit261 of a multiphase meter calibration system 161, according to certainembodiments.

FIG. 3 is an exemplary illustration depicting the circuitry of ameasurement and control unit of a multiphase meter calibration system161, according to certain embodiments.

FIG. 4 is an exemplary illustration depicting the connectivity andcircuitry of components of a multiphase meter calibration system 161,according to certain embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to the drawings, wherein, like reference numeralsdesignate identical or corresponding parts throughout the several views.

Briefly, the multiphase meter calibration system 161 as designed is aclosed loop system which consists mainly of an oil-water gravityseparator 100, oil (116) and water (114) flow meters, a test section forthe multiphase meter to be calibrated 180, a single phase pipeline 311or flow loop section containing the flow calibration square tank 200,manual (106, 108, 110 112, 204) and solenoid (118, 206, 208) valves, andpumps (102, 104, 210). All of these components are connected through thepiping system and valves. The designed multiphase meter calibrationsystem as described herein has a two-step calibration process fordifferent fluid flow rates and/or water cuts. In the first calibrationstep, the single phase oil (116) and water (114) flow meters arecalibrated separately using the single phase pipeline 311 or flow loopsection by monitoring the single phase fluid level rise in thecalibration tank 200 on a real time basis using a fluid level sensor 202and/or a fluid level sighting glass 212. The second step involves thecalibration of the multiphase meter to be calibrated for variable fluidflow rates and/or water cuts using the two pre-calibrated single phaseflow meters (114, 116). The multiphase fluid moves in a closed loop andis separated into distinct phases by the oil-water gravity separator100.

A microprocessor based data acquisition system 400 is used forprocessing the collected data from the single phase meters (114, 116)and the multiphase meter to be calibrated 180 and from the fluid levelsensor 202 to calibrate the flow meters. A programmable logic controller500 is used to control the solenoid valves and pumps during the singlephase and multiphase calibration processes. A flow controller 600 isused to control the oil and water pumps speed for predefined fluid flowrates. The system has the option of choosing three different types ofcalibration processes (001, 002, 003) from the measurement and controlpanel.

The multiphase meter calibration system described herein accuratelycalibrates multiphase meters such as a multiphase flow meter or watercut meter. The multiphase flow parameters may be displayed in a realtime basis, such as on a screen of the microprocessor based dataacquisition system 400. The programmable logic controller 500 takesfeedback from the data acquisition system and operates the solenoidvalves (118, 206, 208) and the variable flow pumps (102, 104)accordingly for single phase and multiphase flow calibration processesas set by the calibration option (001, 002, 003) from the measurementand control panel. A flow controller (600) takes feedback from the waterand oil flow meters (114, 116) to control the speed of the water and oilpumps (102, 104) based on the predefined, predetermined and/orprecalibrated single phase fluid flow rates.

FIG. 1 is an exemplary illustration of a multiphase meter calibrationsystem 161.

According to a first aspect, the present disclosure relates to a closedloop system 161 for calibration of a multiphase meter 180 comprising i)a separation vessel 100, comprising a first compartment for containingseparated water and a second compartment for containing separated oil,ii) a first junction located downstream of the separation vessel 100having a first input, a second input, and an output, iii) a waterpipeline configured to receive water from the first compartment anddeliver it to the first input of the first junction, iv) an oil pipelineconfigured to receive oil from the second compartment and deliver it tothe second input of the first junction, v) a multiphase meter sectioncomprising the multiphase meter to be calibrated 180 located downstreamof the output of the first junction, vi) a second junction 301 locateddownstream of the multiphase meter section having an input configured toreceive water, oil or both from the multiphase meter section, a firstoutput and a second output, vii) a single phase calibration unit 261located downstream of the second junction 301 and upstream of theseparation vessel 100, viii) a single phase pipeline 311 locateddownstream of the second junction 301 configured to receive water or oilfrom the first output of the second junction and deliver it to theseparation vessel 100 through the single phase calibration unit 261, andix) a multiphase collecting pipeline located downstream of the secondjunction configured to receive water, oil or both from the second outputof the second junction and deliver it to the separation vessel 100without passing through the single phase calibration unit 261, whereinthe separation vessel 100, the first junction, the multiphase metersection, the second junction, and the single phase calibration unit 261are fluidly connected, wherein the water pipeline and oil pipeline areconnected in parallel between the separation vessel 100 and the firstjunction, and wherein the single phase pipeline 311 and the multiphasecollecting pipeline are connected in parallel to the second junction301.

The system components may be directly connected or fluidly connected toone another, for example, by connecting pipes or pipelines withoutintervening components. In addition, one or more valves, meters, orpumps may be disposed in a variety of ways, for example, betweenportions of connecting pipes, or for example, integrally to anyadditional or other system components. These pipes, valves, meters, andpumps may control and monitor the flow of fluid through the closed loopcalibration system. Depending on the size and/or intended use of themultiphase meter calibration system described herein the internaldiameters of the connecting pipes and valves may range from 5-100 mm,preferably 10-60 mm, preferably 15-50 mm, preferably 20-40 mm, althoughthe internal diameters of the connecting pipes and valves may bevariable.

As used herein, “multiphase flow” refers to the simultaneous flow ofmaterials with different states or phases (i.e. gas, liquid, or solid)and/or materials with different chemical properties but in the samestate of phase (i.e. liquid-liquid systems such as oil in water). Phasemay refer to thermodynamic systems throughout which all physicalproperties of a given material are essentially uniform. Each of thephases is considered to have a separately defined volume fraction (thesum of which is unity) and velocity field. In a preferred embodiment,this definition includes the flow of two more thermodynamicallyincompatible phases with state of aggregation (i.e. an aqueous phase andan organic phase), more preferably water (an aqueous phase) and oil (anorganic phase). As used herein oil refers to any neutral, nonpolarchemical substance that is a viscous liquid at ambient temperatures andis both hydrophobic and lipophilic, generally having a high carbon andhydrogen content and preferably petrochemical in origin. This type offluid flow may be encountered in numerous industrial processesincluding, but not limited to, riser reactors, bubble bed columnreactors, fluidized bed reactors, dryers and preferably oil productionfluids.

As used herein the term “multiphase meter” refers to a device used tomeasure characteristics of a given multiphase material. In a preferredembodiment, the multiphase meter to be calibrated is a multiphase flowmeter. As used herein a multiphase flow meter refers to a device used tomeasure the individual phase flow rates of constituent phases in a givenflow, such as, for example oil and water in the petroleum industry. In apreferred embodiment, the multiphase meter to be calibrated is a watercut meter. As used herein a water cut meter (or online waterdetermination meter) refers to a device used to measure the watercontent (or cut) of crude oil and hydrocarbons as they flow through apipeline. Due to maintenance or high usage, multiphase meters need to becalibrated. Calibration can be defined as the process of referencingsignals of known quantity that have been predetermined to suit the rangeof measurements required. Calibration can also refer to the mathematicaloperation whereby multiphase meters are standardized by determining thedeviation from the predetermined standard so as to ascertain the propercorrection factors. In determining the deviation from the predeterminedstandard, the actual multiphase measurement must be first determined. Asdescribed herein, the multiphase meter is calibrated by determiningcorrection factors which relate the measurements of a multiphase meteror stream to the individual measurements made by similar meters ordevices in each of the separated phases. This calibration may beperformed in the factory where the multiphase meter is produced, in atest facility including several options for where the multiphase metermay be tested or preferably “in-situ” denoting calibration of amultiphase meter at the location or final destination where themultiphase meter is going to be put into service.

In a preferred embodiment, the multiphase meter calibration systemdescribed herein comprises a separation vessel 100 comprising a firstcompartment for containing separated water and a second compartment forcontaining separated oil. As used herein, a separation vessel or oilwater separator refers to a piece of equipment used to separate oil andwater mixtures into their separate components. The term separator orseparation vessel in oilfield or petroleum production terminologydesignates a vessel designed and used for separating production fluidsinto their constituent components, such as oil and water. A separationvessel may be referred to in the following ways: oil and waterseparator, oil and gas separator, separator, stage separator, trap,knockout vessel (knockout drum, knockout trap, water knockout or liquidknockout), flash chamber (flash vessel or flash trap), expansionseparator, expansion vessel, scrubber, and/or filter.

Separators can be classified by function. Separators are available fortwo phase operation and three phase operation. In two phase units, gasis separated from liquid (i.e. oil or water) with the gas and liquidbeing discharged separately or one liquid is separated from a secondliquid (i.e. oil and water). In three phase separators, well fluid isseparated into gas, oil, and water with the three fluids beingdischarged separately. Separators can be classified by operatingconfiguration. Separators have three general configurations: vertical,horizontal and spherical. Horizontal separators may be manufactured withmonotube units having one cylindrical shell and dual tube units havingtwo cylindrical parallel shells. In terms of the present disclosure theseparation vessel may be two phase, three phase, horizontal, vertical,spherical, monotube or dualtube, and mixtures thereof. Exemplarysuitable types of weirs include, but are not limited to, testseparators, production separators, low temperature separators, meteringseparators and the like. In a preferred embodiment, the separationvessel has an operation pressure of less than 300 psi, preferably lessthan 200 psi, preferably less than 100 psi, preferably less than 50 psi,preferably less than 25 psi, preferably less than 20 psi, preferablyless than 15 psi, such as for example 14.7 psi.

The separation vessel may be constructed of a material, such as metal,plastic, ceramic or glass that can withstand the temperatures andpressures of storing and separating the multiphase fluid and that iscompatible with the multiphase fluid employed in the system. The volume,dimensions, temperature and insulation characteristics of the separationvessel are based on design operational capabilities of the multiphasemeter calibration system described herein.

In a preferred embodiment, separation vessel 100 is a an oil-watergravity separator in the form of a cylindrical horizontal tank having adiameter in the range of 0.2-5.0 m, preferably 0.5-4.0 m, preferably0.6-3.0 m, preferably 0.7-2.0 m, preferably 0.8-1.5 m, preferably0.9-1.2 m and a seam to seam (S to S) length of 0.5-30 m, preferably1.0-25 m, preferably 2.5-20 m, preferably 5.0-18 m, preferably 7.5-15 m,preferably 8-12 m. In one embodiment, the separation vessel has a totalvolume of 100-20000 L, preferably 500-18000 L, preferably 1000-15000 L,preferably 2500-12000 L, preferably 5000-10000 L, preferably 6000-9000L, preferably 7000-8000 L depending on the demands of the system. Theoil-water gravity separator is divided into oil and water portions orcompartments (i.e. the first compartment and the second compartment)separated by a weir 120 having a height of 0.5-0.8 times the diameter ofthe cylinder, preferably 0.55-0.75, preferably 0.60-0.70 times,preferably 0.64-0.68 times or about 0.66 times the diameter of thecylinder. The return fluid (i.e. water or oil from the single phasecalibration unit and/or water, oil, or both from the multiphasecollecting pipeline) flows back to the separation vessel, preferably thefirst compartment water side during the calibration process. As a resultof gravity, the water stays on the water side (i.e. first compartment)of the tank, and the oil, being lighter than water, flows to the oilportion side (i.e. second compartment) of the tank. This oil-waterseparation method is called gravity separation and is a continuousoil-water separation process. The multiphase fluid of the presentdisclosure moves in a closed loop and is separated into distinct phasesby the oil-water gravity separator 100.

As used herein, a weir refers to a barriers across a fluid designed toalter its flow characteristics. In most cases, weirs take the form ofobstructions that pool fluid (i.e. water) behind them while alsoallowing it to flow steadily over their tops (i.e. lighter oil).Exemplary suitable types of weirs include, but are not limited to, alabyrinth weir, a broad-crested weir, a sharp crested weir (fayoumweir), a piano keys weir (PKW), a compound weir, a V-notch weir, and thelike, and mixtures thereof.

It is equally envisaged that the multiphase meter calibration system ofthe present disclosure may be adapted to comprise other separationvessels. Exemplary suitable oil-water separators include, but are notlimited to, an API oil water separator, a marine oily water separator, adownhole oil water separator, a gravity plate separator, anelectrochemical separator, a bioremediation separator, a centrifugaloily water separator and the like. For example an API oil waterseparator. An API oil water separator is a device designed to separategross amounts of oil from water effluents of oil refineries,petrochemical plants, chemical plants, natural gas processing plants andother industrial sources, they are designed according to standards ofthe American Petroleum Institute (API). The API separator is a gravityseparation device designed by using Stokes' law to define the risevelocity of oil droplets based on their density and size, the design ofthe separator is based on the specific gravity difference between theoil and the water.

In a preferred embodiment, the water pipeline comprises a variable flowwater pump downstream of the first compartment and a water flow meterdownstream of the variable flow water pump and the oil pipelinecomprises a variable flow oil pump downstream of the second compartmentand an oil flow meter downstream of the variable flow oil pump. In apreferred embodiment, the water pipeline further comprises one or morevalves located downstream of the water flow meter, upstream of thevariable flow water pump or both and the oil pipeline further comprisesone or more valves located downstream of the oil flow meter, upstream ofthe variable flow oil pump or both.

As used herein, a pump refers to a device that moves fluids (i.e.liquids) by mechanical action. Pumps can be classified into three majorgroups according to the method they use to move the fluid: direct lift,displacement, and gravity pumps. Pumps operate by a mechanism (i.e.reciprocating or rotary) and consume energy to perform mechanical workby moving the fluid. Pumps operate via many energy sources includingmanual operation, electricity and engines and com in many sizes frommicroscopic to large industrial pumps. Exemplary acceptable water and/oroil pumps include, but are not limited to, positive displacement pumps(rotary, reciprocating, linear), impulse pumps, velocity pumps, gravitypumps, steam pumps, valveless pumps, centrifugal pumps, gear pumps,screw pumps, rotary vane pumps, plunger pumps, diaphragm pumps, pistonpumps, radial piston pumps, rotary lobe pumps, progressive cavity pumps,rotary gear pumps, hydraulic pumps, peristaltic pumps, rope pumps,flexible impeller pumps, radial flow pumps, axial flow pumps, mixed flowpumps, educator jet pumps, and the like. In a preferred embodiment, thewater pipeline and the oil pipeline comprise variable flow pumps,preferably variable displacement pumps. As used herein a variabledisplacement pump is a device that converts mechanical energy tohydraulic (fluid) energy. The displacement, or amount of fluid pumpedper revolution of the pump's input shaft can be varied while the pump isrunning.

As used herein, a flow meter is a device for flow measurement or thequantification of bulk fluid movement. Flow can be measured in a varietyof ways. Positive displacement flow meters accumulated a fixed volume offluid and then count the number of times the volume is filled to measureflow. Other flow measurement methods rely on forces produced by theflowing stream as it overcomes a known constriction, to indirectlycalculate flow. Flow may be measured by measuring the velocity of fluidover a known area. Exemplary acceptable water and/or oil flow metersinclude, but are not limited to, mechanical flow meters, pistonmeter/rotary pistons, oval gear meters, gear meters, helical gearmeters, nutatitng disk meters, variable area meters, turbine flowmeters, woltman meters, single jet meters, paddle wheel meters, multiplejet meters, pelton wheel meters, current meters, pressure based meters,venture meters, orifice plate meters, dall tube meters, pitot-statictube meters, multi-hole pressure probe meters, cone meters, linearresistance meters, optical flow meters, open-channel flow meters,thermal mass flow meters, vortex flow meters, electromagnetic flowmeters, ultrasonic flow meters, coriolis flow meters, laser Doppler flowmeters and the like.

As used herein, a valve is a device that regulates, directs or controlsthe flow of a fluid (gases, liquid, fluidized solids or slurries) byopening, closing or partially obstructing various passageways. In anopen valve, fluid flows in a direction from higher pressure to lowerpressure. Valves vary widely in form, size and application. Valves arequite diverse and may be classified into a number of acceptableexemplary basic types including, but not limited to hydraulic,pneumatic, manual, solenoid and motor. The main parts of the most usualtypes of valves are the body and the bonnet. These two parts form thecasing that holds the fluid going through the valve. Additional valvecomponents may include, but are not limited to, body, bonnet, ports,handle or actuator, disc, seat, stem, gaskets, valve balls, spring andtrim and each part exists in several types and designs.

In a preferred embodiment, the water pipeline and the oil pipelinecomprise gate valves. As used herein, a gate valve (sluice valve) is avalve that opens by lifting a round or rectangular gate/wedge out of thepath of the fluid. The distinct feature of a gate valve is the sealingsurfaces between the gate and seats are planar, so gate valves are oftenused when a straight-line flow of fluid and minimum restriction isdesired. Gate valves are primarily used to permit or prevent the flow ofliquids and their ability to cut through liquids allow them to often beused in the petroleum industry. The gate valves may have a rising ornon-rising stem and a screw-in, union, bolted, or pressure sealedbonnet.

FIG. 2 is an exemplary illustration of the single phase calibration unit261.

In a preferred embodiment the single phase calibration unit 261comprises i) a calibration tank 200 having a fluid reference level and amaximum fluid level configured to collect an amount of water or anamount of oil from the single phase pipeline 311, ii) a fluid levelsensor 202 configured to detect a level of water or a level of oil inthe calibration tank 200, and iii) a fluid level sighting glass 212configured to visualize a level of water or a level of oil in thecalibration tank.

The calibration unit may be constructed of a material, such as metal,plastic, ceramic or glass that can withstand the temperatures andpressures of receiving and measuring the single phase fluid and that iscompatible with the single phase fluids employed in the system. Thevolume, dimensions, temperature and insulation characteristics of thecalibration tank 200 are based on design operational capabilities of themultiphase meter calibration system described herein. In a preferredembodiment, the calibration tank 200 is square in cross section and hasa volume in the range of 0.1-1.0 times the volume of the separationvessel, preferably 0.2-0.75, preferably 0.3-0.6, preferably 0.35-0.5times the volume of the separation vessel.

The single phase flow calibration section of the flow loop is used forcalibration of water and oil flow meters (114, 116). It consists of asingle phase flow calibration tank 200, fluid level sensor 202, fluiddrain gate valve 204, inlet and outlet solenoid valves (206, 208), fluidreturn pump 210, fluid level sighting glass 212, and a removable lid214. In a preferred embodiment, the removable lid 214 and the drain gatevalve 204 are used for cleaning and maintenance of the calibration tank.In a preferred embodiment, the fluid level sighting glass 212 is usedfor manual monitoring of fluid level in the calibration tank. In certainembodiments, the air vent 216 is provided as a measure for the pressurerelief inside the tank. In a preferred embodiment, the calibration tankcontains the fluid level sensor 202 for monitoring the fluid level inthe tank on a real time basis. The fluid level sensor monitors the fluidlevel from the reference level to the maximum level in the tank. Thefluid level in the calibration tank is recorded automatically on a realtime basis by the data acquisition system 400 for different fluid flowrates. Exemplary fluid level sensors include, but are not limited to,point level detection of liquids (magnetic and mechanical float,pneumatic, conductive), both point level detection or continuousmonitoring (ultrasonic, capacitance, optical interface, microwave), andcontinuous level measurement (magnetostrictive, resistive chain,magnetoresistive, hydrostatic pressure, air bubbler, gamma ray) and thelike.

Before initiating a single phase calibration process, the calibrationtank 200 needs to be emptied by opening the solenoid valve 208 andrunning the return fluid pump 210. During the single phase flow metercalibration, the inlet solenoid valve 206 is opened and the outletsolenoid valve 208 remains closed. The fluid level sensor 202 isconnected to the data acquisition system 400 for recording the fluidlevel in the calibration tank 200 on a real time basis. Once the maximumfluid level is reached in the calibration tank, the data acquisitionsystem sends the signal to the programmable logic controller 500 whichstops the pump (102 or 104) and closes the inlet solenoid valve (206).

In a preferred embodiment, the single phase pipeline 311 furthercomprises at least one solenoid valve located upstream of the singlephase calibration unit and the multiphase collecting pipeline furthercomprises at least one solenoid valve located upstream of the separationvessel. In a preferred embodiment, the multiphase meter calibrationsystem further comprises a third junction located downstream of thesingle phase calibration unit having a first input configured to receivewater or oil from the single phase pipeline 311, a second inputconfigured to receive water, oil, or both from the multiphase collectingpipeline, and an output configured to deliver water, oil, or both to theseparation vessel. In a preferred embodiment, the single phase pipeline311 further comprises a fixed flow fluid return pump located downstreamof the single phase calibration unit and upstream of the third junction.In a preferred embodiment, the single phase pipeline further comprisesat least one solenoid valve located downstream of the single phasecalibration unit and upstream of the fixed flow fluid return pump.

As used herein, a solenoid valve refers to an electromechanicallyoperated valve. The valve is controlled by an electric current through asolenoid: in the case of a two-port valve the flow is switched on oroff. Solenoid valves are the most frequently used elements in fluidics.Their tasks are to shut off, release, dose, distribute or mix fluids.They are found in many application areas. Solenoids offer fast and safeswitching, high reliability, long service life, good mediumcompatibility of the materials used, low control power and compactdesign. In addition to the plunger type actuator which is used mostfrequently, pivoted armature actuators and rocker actuators are alsoused. In certain embodiments, the solenoid valves may be internallypiloted. Solenoid valve designs have many variations and challenges,common components of a solenoid valve include, but are not limited to,solenoid subassembly (retaining clip, coil clip, solenoid coil, magneticreturn path, core tube, armature tube, plunger tube, solenoid valvetube, sleeve, guide assembly, plugnut, fixed core, shading coil, shadingring, core spring, counter spring, core, plunger, armature), coretube-bonnet seal, bonnet (cover), bonnet diaphragm body seal, hangerspring, backup washer, diaphragm (bleed hole), disk, and valve body(seat). The valve body and seals must be compatible with the fluid (i.e.water and oil) and common materials include, but are not limited to,brass, stainless steel, aluminum and plastic. The solenoid valves of thepresent disclosure may be one- or two-solenoid valves, direct current oralternating current powered, and encompass a wide number of ways andpositions.

In a preferred embodiment, the fixed flow fluid return pump is a fixeddisplacement pump, in which the displacement or flow through the pumpper rotation or revolution of the pump cannot be adjusted.

In a preferred embodiment, the multiphase meter calibration systemfurther comprises a data acquisition unit comprising a microprocessorconfigured to collect and process data from and electronically connectedto at least one of the water flow meter, the oil flow meter, the fluidlevel sensor of the single phase calibration unit and the multiphasesection comprising the multiphase meter to be calibrated. In a preferredembodiment, the multiphase meter calibration system further comprises aflow controller configured to control the speed of at least one of thevariable flow water pump and the variable flow oil pump and receive datafrom at least one of the water flow meter and the oil flow meter. In apreferred embodiment, the multiphase meter calibration system furthercomprises a programmable logic controller configured to control theoperation of at least one of the variable flow water pump, the variableflow oil pump, the fixed flow fluid return pump, and at least one of thesolenoid valves.

In certain embodiments, the calibration system comprises a measurementand control unit and/or data acquisition unit in the form of a computer.FIG. 3 is an exemplary illustration of a computer that acts as themeasurement and control unit and/or a data acquisition unit comprising amicroprocessor. FIG. 4 is an exemplary illustration depicting theconnectivity of components of the multiphase meter calibration system161.

A hardware description of the computer according to exemplaryembodiments is described with reference to FIG. 3. In FIG. 3, thecomputer includes a CPU 300 which performs the processes describedherein. The process data and instructions may be stored in memory 302.These processes and instructions may also be stored on a storage mediumdisk 304 such as a hard drive (HDD) or portable storage medium or may bestored remotely. Further, the claimed advancements are not limited bythe form of the computer readable media on which the instructions of theinventive process are stored. For example, the instructions may bestored on CDs, DVDs, in FLASH memory, RAM, ROM, PROM, EPROM, EEPROM,hard disk or any other information processing device with which thecomputer communicates, such as a server or computer.

Further, the claimed advancements may be provided as a utilityapplication, background daemon, or component of an operating system suchas Microsoft Windows, UNIX, Solaris, LINUX, Apple MAC-OS and othersystems known to those of ordinary skill in the art.

The hardware elements in order to achieve the computer may be realizedby various circuitry elements, known to those of ordinary skill in theart. For example, CPU 300 may be a Xenon or Core processor from Intel ofAmerica or an Opteron processor from AMD of America, or may be otherprocessor types that would be recognized by one of ordinary skill in theart. Alternatively, the CPU 300 may be implemented on an FPGA, ASIC, PLDor using discrete logic circuits, as one of ordinary skill in the artwould recognize. Further, CPU 300 may be implemented as multipleprocessors cooperatively working in parallel to perform the instructionsof the inventive process described herein.

The computer in FIG. 3 also includes a network controller 306, such asan Intel Ethernet PRO network interface card from Intel Corporation ofAmerica, for interfacing with network 330. As can be appreciated, thenetwork 330 can be a public network, such as the Internet, or a privatenetwork such as an LAN or WAN network, or any combination thereof andcan also include PSTN or ISDN sub-networks. The network 330 can also bewired, such as an Ethernet network, or can be wireless such as acellular network including EDGE, 3G and 4G wireless cellular systems.The wireless network can also be WiFi, Bluetooth, or any other wirelessform of communication that is known.

The computer further includes a display controller 308, such as a NVIDIAGeForce GTX or Quadro graphics adaptor from NVIDIA Corporation ofAmerica for interfacing with display 310, such as a Hewlett PackardHPL2445w LCD monitor. A general purpose I/O interface 312 interfaceswith a keyboard and/or mouse 314 as well as a touch screen panel 316 onor separate from display 310. The general purpose I/O interface alsoconnects to a variety of peripherals 318 including printers andscanners, such as an OfficeJet or DeskJet from Hewlett Packard.

A sound controller 320 is also provided in the computer, such as SoundBlaster X-Fi Titanium from Creative, to interface withspeakers/microphone 322 thereby providing sounds and or music.

The general purpose storage controller 324 connects the storage mediumdisk 304 with communication bus 326, which may be an ISA, EISA, VESA,PCI, or similar, for interconnecting all of the components of thecomputer. A description of the general features and functionality of thedisplay 310, keyboard and/or mouse 314, as well as the displaycontroller 308, storage controller 324, network controller 306, soundcontroller 320, and general purpose I/O interface 312 is omitted hereinfor brevity as these features are known to those of ordinary skill inthe art.

In a preferred embodiment, the multiphase meter calibration systemfurther comprises a data acquisition unit comprising a microprocessor.The water and oil flow meters (114, 116), a multiphase meter, such as amultiphase flow meter or water cut meter (180), and a fluid level sensor202 are connected to the microprocessor based data acquisition system400. In a preferred embodiment, the multiphase meter calibration systemfurther comprises a programmable logic controller. The programmablelogic controller 500 is used to control the ON/OFF operation of thepumps (102, 104, 210) and the solenoid valves (118, 206, 208). Thecontroller takes feedback from the calibration options (001, 002, 003)and from the fluid level sensor 202 to operate the pumps and solenoidvalves accordingly.

As used herein, a programmable logic controller (PLC) or programmablecontroller refers to a digital computer used for automation of typicallyindustrial electromechanical processes. Programmable logic controllersmay be used in many machines, in many industries. Programmable logiccontrollers are designed for multiple arrangements of digital and analoginputs and outputs, extended temperature ranges, immunity to electricalnoise, and resistance to vibration and impact. Programs to controlmachine operations are typically stored in battery back-up ornonvolatile memory. A programmable logic controller is an example of a“hard” real time system since output results must be produced inresponse to input conditions within a limited time, otherwise unintendedoperation will result.

In a preferred embodiment, the multiphase meter calibration system asdescribed herein further comprises a flow controller. In a preferredembodiment, the flow controller 600 is used to control the speed of thevariable flow pumps (102, 104) based on the signal received from thewater and oil flow meters (114, 116). The flow controller has the optionof selecting the desired oil and water flow rates.

As used herein a flow controller refers to a device used to measureand/or control the flow of liquids and gases. In certain embodiments,the flow controller may be a mass flow controller (MFC). A mass flowcontroller is designed and calibrated to control one or more specifictypes of liquids or gasses in a particular range of flow rates. The massflow controller can be given a set point from 0% to 100% of its fullscale range but is typically operated in the 10% to 90% of its fullscale range where the best accuracy is achieved. The device will thencontrol the rate of flow to the given set point. In certain embodiments,the flow controller may be either analog or digital. A digital flowcontroller may be advantageous as it is usually able to control morethan one type of fluid whereas in some instances an analog flowcontroller is limited to the fluid for which it has been calibrated.

In certain embodiments, a mass flow controller may comprise an inletport, an outlet port, a mass flow sensor and a proportional controlvalve. The mass flow controller may be fitted with a closed loop controlsystem which is given an input signal by the operator (or an externalcircuit/computer) the it compares to the value from the mass flow sensorand adjusts the proportional valve accordingly to achieve the requiredflow. The flow rate may be specified as a percentage of its calibratedfull scale flow and may be supplied to the mass flow controller as avoltage signal. Often, mass flow controllers require the supply ofliquid (or gas) to be within a specific pressure range. Low pressure maystarve the mass flow controller causing it to fail to achieve its setpoint. High pressure may cause erratic flow rates.

The below is an exemplary operation of the multiphase meter calibrationsystem described herein. The exemplary operation procedure is intendedto further illustrate methods and protocols for operating the system andcalibrating a multiphase meter, such as a multiphase flow meter or watercut meter. It is not intended to limit the scope of the claims.

In certain embodiments, the following steps are to be used for thecalibration of a multiphase meter such as a multiphase flow meter or awater cut meter employing the closed loop system for calibration of amultiphase meter 161 described herein in any of its embodiments. Thecalibration of the single phase flow meters is done for water and oilflow meters (114, 116) separately using the single phase pipeline orflow loop section of the designed calibration system. The single-phasecalibration option uses the single phase flow calibration tank 200 forthe monitoring of fluid flow rates. The manual gate valves (106, 112)are provided for safety reasons and in some embodiments may always bekept in open positions. The drain gate valve 204 in preferredembodiments may always be kept in a closed position unless the cleaningof the calibration tank 200 requires it to be opened.

In certain embodiments, the following steps are to be used for thecalibration of the water flow meter 114 of the closed loop system forcalibration of a multiphase meter 161 described herein in any of itsembodiments. Before starting the calibration of the water flow meter 114all solenoid valves (118, 206, 208) are kept in a closed position,preferably by the programmable logic controller 500. The gate valves(106, 108) should remain in an open position while the gate valves (110,112) are in a closed position. The desired water flow rate should be setin the flow controller 600 and the water flow meter calibration option(001) should be selected from the measurement and control unit of thecalibration system.

Based on the selection of the water flow meter calibration option (001),the programmable logic controller 500 takes the feedback signal from thefluid level sensor 202 and checks the fluid level in the calibrationtank 200. If the fluid level in the tank is above the fluid referencelevel, the logic controller opens the solenoid valve 208 and starts thereturn fluid pump 210. Once the fluid level falls below the referencelevel in the tank, it closes the solenoid valve 208 and stops the pump210. Subsequently, or if initially the fluid level in the tank is belowthe reference level, the logic controller 500 opens the solenoid valve118 and starts the variable flow water pump 102. The water pump 102draws water from the first compartment of the separation vessel 100,preferably an oil-water gravity separator and pumps it through the waterpipeline containing the water flow meter 114, the multiphase metersection, and the multiphase collecting pipeline.

Once the desired water flow rate is achieved by the flow controller 600it sends the signal to the logic controller 500 which closes thesolenoid valve 118 and opens the inlet solenoid valve 206 of the singlephase pipeline. The water then enters the single phase calibration unit261, specifically the calibration tank 200. Once water enters thecalibration tank 200 the data acquisition system 400 records thereal-time data from the fluid level sensor 202 and the water flow meter114. Once the maximum fluid level is reached in the tank, the dataacquisition system 400 sends the signal to the programmable logiccontroller 500 which stops the pump 102 and closes the inlet solenoidvalve 206.

For additional water flow rates, a plurality of desired water flow ratescan be selected and the above described procedure repeated until a fullrange of water flow rates for the water flow meter 114 has been covered.The experimental real time data for the plurality of water flow ratesrecorded by the data acquisition system 400 from the fluid level sensor202 may be plotted against the data obtained from the water flow meter114 to generate a calibration constant for the water flow meter 114. Themeasured water volume flow rate (V_(w)) for a fixed speed of thevariable flow pump 102 can be expressed by an equation of formula (I).

$\begin{matrix}{V_{w} = \frac{\Delta \; h_{w}A}{\Delta \; t}} & (I)\end{matrix}$

In this equation Δh_(x)=h_(2w)−h_(1w), V_(w) is the water volume flowrate for a fixed pump speed in m³/s, Δh_(w) is the rise in water level(in meters) in the calibration tank during the time interval Δt (t₂−t₁)in seconds and A is the cross sectional area of the calibration tank(200) in m². For different set speeds of the water pump 102, the actualwater volume flow rate can be obtained from the equation of formula (I).The measured water flow rates and data obtained by varying the speed ofthe water pump 102 is compared with data obtained from the water flowmeter 114. The water flow meter 114 data may be plotted versus themeasured water flow rates data and a calibration constant of the waterflow meter 114 determined.

In certain embodiments, the following steps are to be used for thecalibration of the oil flow meter 116 of the closed loop system forcalibration of a multiphase meter 161 described herein in any of itsembodiments. Before starting the calibration of the oil flow meter 116all solenoid valves (118, 206, 208) are kept in a closed position,preferably by the programmable logic controller 500. The gate valves(106, 108) should remain in a closed position while the gate valves(110, 112) are in an open position. The desired oil flow rate should beset in the flow controller 600 and the oil flow meter calibration option(002) should be selected from the measurement and control unit of thecalibration system.

Based on the selection of the oil flow meter calibration option (002),the programmable logic controller 500 takes the feedback signal from thefluid level sensor 202 and checks the fluid level in the calibrationtank 200. If the fluid level in the tank is above the fluid referencelevel, the logic controller opens the solenoid valve 208 and starts thereturn fluid pump 210. Once the fluid level falls below the referencelevel in the tank, it closes the solenoid valve 208 and stops the pump210. Subsequently, or if initially the fluid level in the tank is belowthe reference level, the logic controller 500 opens the solenoid valve118 and starts the variable flow oil pump 104. The oil pump 104 drawsoil from the second compartment of the separation vessel 100, preferablyan oil-water gravity separator and pumps it through the oil pipelinecontaining the oil flow meter 116, the multiphase meter section, and themultiphase collecting pipeline.

Once the desired oil flow rate is achieved by the flow controller 600 itsends the signal to the logic controller 500 which closes the solenoidvalve 118 and opens the inlet solenoid valve 206 of the single phasepipeline. The oil then enters the single phase calibration unit 261,specifically the calibration tank 200. Once oil enters the calibrationtank 200 the data acquisition system 400 records the real-time data fromthe fluid level sensor 202 and the oil flow meter 116. Once the maximumfluid level is reached in the tank, the data acquisition system 400sends the signal to the programmable logic controller 500 which stopsthe pump 104 and closes the inlet solenoid valve 206.

For additional oil flow rates, a plurality of desired oil flow rates canbe selected and the above described procedure repeated until a fullrange of oil flow rates for the oil flow meter 116 has been covered. Theexperimental real time data for the plurality of oil flow rates recordedby the data acquisition system 400 from the fluid level sensor 202 maybe plotted against the data obtained from the oil flow meter 116 togenerate a calibration constant for the oil flow meter 116. The measuredoil volume flow rate (V_(o)) for a fixed speed of the variable flow pump104 can be expressed by an equation of formula (II).

$\begin{matrix}{V_{o} = \frac{\Delta \; h_{o}A}{\Delta \; t}} & ({II})\end{matrix}$

In this equation Δh_(o)=h_(2o)−h_(1o), V_(o) is the oil volume flow ratefor a fixed pump speed in m³/s, Δh_(o) is the rise in oil level (inmeters) in the calibration tank during the time interval Δt (t₂−t₁) inseconds and A is the cross sectional area of the calibration tank (200)in m². For different set speeds of the oil pump 104, the actual oilvolume flow rate can be obtained from the equation of formula (II). Themeasured oil flow rates and data obtained by varying the speed of theoil pump 104 is compared with data obtained from the oil flow meter 116.The oil flow meter 116 data may be plotted versus the measured oil flowrates data and a calibration constant of the oil flow meter 116determined.

In certain embodiments, the following steps are to be used for thecalibration of a multiphase meter such as a multiphase flow meter or awater cut meter employing the closed loop system for calibration of amultiphase meter 161 described herein in any of its embodiments. In apreferred embodiment, the multiphase flow meter or water cut metercalibration is carried out by using the pre-calibrated single phasewater flow meter 114, the pre-calibrated single phase oil flow meter 116or both as previously described herein. A test section in the multiphasemeter section may be installed comprising a multiphase meter to becalibrated 180, preferably a multiphase flow meter or water cut meter.

Before starting the calibration of the multiphase flow meter or watercut meter the gate valves (106, 108, 110, 112) are to be kept in theopen position. The solenoid valve 118 is to be kept in an open position,preferably by the programmable logic controller 500 and the solenoidvalves (206, 208) are to remain in a closed position during thecalibration process. The desired multiphase fluid mixture flow rate orwater cut should be set in the flow controller 600 and the multiphasemeter calibration option (003) should be selected from the measurementand control unit of the calibration system.

Based on the selection of the multiphase meter calibration option (003),the variable flow water pump 102 draws water from first compartment ofthe separation vessel 100 and the variable flow oil pump 104 draws oilfrom the second compartment of the separation vessel 100 and flows thewater through the water pipeline and oil through the oil pipelinethrough the first junction and into the multiphase meter sectioncomprising the multiphase meter to be calibrated 180. Once the desiredmultiphase fluid mixture flow rate or water cut is achieved by the flowcontroller 600 it sends the signal to the programmable logic controller500 to instruct the data acquisition system 400 to record the real timedata of the single phase water flow meter 114 and the single phase oilmeter 116 together with that of the multiphase meter to be calibrated180. For additional multiphase fluid mixture flow rates or water cuts, aplurality of desired multiphase fluid mixture flow rates or water cutscan be selected and the above described procedure repeated until a fullrange of multiphase fluid mixture flow rates or water cuts for themultiphase meter to be calibrated 180 has been covered. The experimentaldata, for the plurality of multiphase fluid mixture flow rates or watercuts recorded by the data acquisition system 400 from the water and oilflow meters (114, 116) may be plotted against the data obtained from themultiphase flow meter or water cut meter to be calibrated 180 togenerate a calibration constant for the multiphase flow meter or watercut meter to be calibrated 180.

For an exemplary water cut meter, the water cut (λ) is the volumefraction of water in a multiphase fluid mixture. For homogenous flow andfor a fixed speed of the flow pumps (102, 104), the water cut (λ) can beexpressed by an equation of formula (III).

$\begin{matrix}{\lambda = \frac{V_{w}}{V_{w} + V_{o}}} & ({III})\end{matrix}$

In this equation λ, is the water cut, V_(w) is the water volume flowrate from the water flow meter (114) in m³/s and V_(o) is the oil volumeflow rate from the oil flow meter (116) in m³/s. The pre-calibratedwater flow meter 114 and oil flow meter 116 data can be used tocalculate the water cuts for different speeds of the water flow pump 102and the oil flow pump 104 from the equation of formula (III). Themeasured water cuts data obtained by varying the speed of the water pump102 and the oil pump 104 is compared with the data obtained from thewater cut meter to be calibrated 180. The water cut meter to becalibrated data may be plotted versus the measured water cuts data and acalibration constant of the water cut meter to be calibrated determined.

For an exemplary multiphase flow meter, the multiphase fluid flow ratemay be determined directly from the pre-calibrated water flow meter 114and oil flow meter 116 and expressed by an equation of formula (IV).

(IV)V _(m) =V _(w) +V _(o)

In this equation V_(m) is the multiphase fluid flow rate in m³/s, V_(w)is the water volume flow rate from the water flow meter (114) in m³/sand V_(o) is the oil volume flow rate from the oil flow meter (116) inm³/s. The measured multiphase fluid flow rates data obtained by varyingthe speed of the water pump 102 and the oil pump 104 is compared withthe data obtained from the multiphase flow meter to be calibrated 180.The multiphase flow meter to be calibrated 180 data may be plottedversus the measured multiphase fluid flow rates data and a calibrationconstant of the multiphase flow meter to be calibrated 180 determined.

According to a second aspect the present disclosure relates to a methodfor calibrating a multiphase meter employing the system of the presentdisclosure described herein in any of its embodiments comprising i)measuring and setting a water flow rate at a predetermined value by flowwater from the first compartment to the single phase calibration unit261 through the multiphase meter section, ii) measuring and setting anoil flow rate at a predetermined value by flowing oil from the secondcompartment to the single phase calibration unit 261 through themultiphase meter section, iii) combining water from the firstcompartment at the predetermined water flow rate value and oil from thesecond compartment at the predetermined flow rate value to form amultiphase stream downstream of the first junction, iv) flowing themultiphase stream through the multiphase meter section to the multiphasecollecting pipeline, v) measuring the flow rate of the multiphase streamby means of the multiphase flow meter to be calibrated, and vi)processing the obtained data of the multiphase stream flow rate alongwith the predetermined water flow rate value and the predetermined oilflow rate value to calculate a calibration correction factor.

In a preferred embodiment, the method further comprises recycling atleast one of the water, the oil and the multiphase stream to theseparation vessel through the single phase pipeline or the multiphasecollecting pipeline. In a preferred embodiment, the method furthercomprises calibrating a single phase water flow meter, a single phaseoil flow meter, or both. In a preferred embodiment, at least one of adata acquisition system, a programmable logic controller and a flowcontroller is used in at least one of the flowing, the measuring, andthe setting of the water flow rate, the oil flow rate, or both. In apreferred embodiment, the multiphase meter to be calibrated is at leastone selected from the group consisting of a multiphase flow meter and awater cut meter.

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, defines, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

1. A closed loop system for calibration of a multiphase meter,comprising: a two phase horizontal oil-water gravity separation vessel,comprising a first compartment for containing water and a secondcompartment for containing oil; a first junction located downstream ofthe separation vessel having a first input, a second input and anoutput; a water pipeline configured to receive water from the firstcompartment and deliver it to the first input of the first junction; anoil pipeline configured to receive oil from the second compartment anddeliver it to the second input of the first junction; a multiphase metersection comprising the multiphase meter to be calibrated locateddownstream of the output of the first junction; a second junctionlocated downstream of the multiphase meter section having an inputconfigured to receive water, oil or both from the multiphase metersection, and having a first output, and a second output; a single phasecalibration unit located downstream of the second junction and upstreamof the separation vessel; a single phase pipeline located downstream ofthe second junction configured to receive water or oil from the firstoutput of the second junction and deliver it to the separation vesselthrough the single phase calibration unit; a multiphase collectingpipeline located downstream of the second junction configured to receivewater, oil or both from the second output of the second junction anddeliver it to the separation vessel without passing through the singlephase calibration unit; wherein the separation vessel, the firstjunction, the multiphase meter section, the second junction and thesingle phase calibration unit are fluidly connected; wherein the waterpipeline and oil pipeline are connected in parallel between theseparation vessel and the first junction; and wherein the single phasepipeline and the multiphase collecting pipeline are connected inparallel to the second junction.
 2. The system of claim 1, wherein themultiphase meter to be calibrated is a multiphase flow meter.
 3. Thesystem of claim 1, wherein the multiphase meter to be calibrated is awater cut meter.
 4. The system of claim 1, wherein the single phasecalibration unit comprises: a calibration tank having a fluid referencelevel and a maximum fluid level configured to collect an amount of wateror an amount of oil from the single phase pipeline; a fluid level sensorconfigured to detect a level of water or a level of oil in thecalibration tank; and a fluid level sighting glass configured tovisualize a level of water or a level of oil in the calibration tank. 5.The system of claim 4, wherein the water pipeline comprises a variableflow water pump downstream of the first compartment and a water flowmeter downstream of the variable flow water pump and the oil pipelinecomprises a variable flow oil pump downstream of the second compartmentand an oil flow meter downstream of the variable flow oil pump.
 6. Thesystem of claim 5, further comprising a data acquisition unit comprisinga microprocessor configured to collect and process data from andelectronically connected to at least one of the water flow meter, theoil flow meter, the fluid level sensor of the single phase calibrationunit and the multiphase section comprising the multiphase meter to becalibrated.
 7. The system of claim 5, further comprising a flowcontroller configured to control the speed of at least one of thevariable flow water pump and the variable flow oil pump and receive datafrom at least one of the water flow meter and the oil flow meter.
 8. Thesystem of claim 5, wherein the single phase pipeline further comprisesat least one solenoid valve located upstream of the single phasecalibration unit and the multiphase collecting pipeline furthercomprises at least one solenoid valve located upstream of the separationvessel.
 9. The system of claim 8, further comprising a third junctionlocated downstream of the single phase calibration unit having a firstinput configured to receive water or oil from the single phase pipeline,a second input configured to receive water, oil or both from themultiphase collecting pipeline, and an output configured to deliverwater, oil or both to the separation vessel.
 10. The system of claim 9,wherein the single phase pipeline further comprises a fixed flow fluidreturn pump located downstream of the single phase calibration unit andupstream of the third junction.
 11. The system of claim 10, wherein thesingle phase pipeline further comprises at least one solenoid valvelocated downstream of the single phase calibration unit and upstream ofthe fixed flow fluid return pump.
 12. The system of claim 11, furthercomprising a programmable logic controller configured to control theoperation at least one of the variable flow water pump, the variableflow oil pump, the fixed flow fluid return pump, and at least one of thesolenoid valves.
 13. The system of claim 5, wherein the water pipelinefurther comprises one or more valves located downstream of the waterflow meter, upstream of the variable flow water pump or both and the oilpipeline further comprises one or more valves located downstream of theoil flow meter, upstream of the variable flow oil pump or both.
 14. Thesystem of claim 1, wherein the separation vessel is a cylindricaloil-water gravity separator and the first compartment and the secondcompartment are separated by a weir having a height of 0.5 to 0.8 timesthe diameter of the cylinder.
 15. The system of claim 2, wherein thesingle phase calibration unit further comprises a drain gate valve and aremovable lid. 16-20. (canceled)